Insulator mounting for transmission lines



Feb. 10, 1942. BATTERMANN 2,272,288

INSULATOR MOUNTING FOR TRANSMISSION LINES- Filed June 24, 1939 INVEN TOR.

ll/D BATTERMANN BY I A TTORNEY.

' centric relationship.

most frequently applied to transmission lines Patented Feb. 10, 1942 INSULATOR MOUNTING FOR TRANSMISSION LINES Ludwig A. Battermann, Rocky Point, N.'Y:, as-

signor to Radio Corporation of America, a corporation of Delaware Application June 24, 1939, Serial No. 280,991

Claims.

This invention relates to a new and novel insulator mounting and is particularly adapted for mounting of an insulator on the inner conductor of a transmission line containing concentric conductors, wherein the inner conductor has a small diameter or comprises a wire or rod.

An object of this invention is to simplify and improve the mounting of insulators for transmission lines with a minimum amount of solid material.

Another object of this invention is to provide an insulator with retaining means which will not appreciably increase the contour of the inner conductor. Still another object of this invention is to improvethe ordinary insulator mounting employed in a coaxial cable having concentric conductors ,forming a transmission line so that the insulating members can be easily moved from one position to another without the use of elaborate tools.

In the radio art, there are numerous occasions for mounting a conductor within a tube to form a coaxial cable which requires insulators placed at intervals to maintain the conductors in con- These applications are having radio frequencies in the order of ten megacycles and above. For the best electrical performance, the insulators should be arranged to provide a minimum amount of solid dielectric material in the electrical field and the contour of the central conductor should not be changr i to any appreciable extent. As the result of the e requirements, I have conceived this invention which comprises briefly a narrow disc-shaped insulator of solid dielectric material having an internal thread with a small pitch in. which is inserted a helical spring which is to-be slipped over the inner conductor.

This invention will best be understood by referring to the accompanying drawing, in which:

Fig. 1 is a cross-section of a coaxial cable;

Fig. 2 is a longitudinal section of Fig. 1;

Fig. 3 is an end elevation of the retaining spring; and. I

Fig. 4 is a side elevation of Fig. 3.

Referring now in detail to the drawing, a central conductor l, which may be in the form of a small metallic rod, wire or tube, has located thereon a plurality of narrow disc-shaped insulators 2', which are of any suitable dielectric material having the requisite insulating qualities and mechanical strength, such as porcelain, Isolantite, or the like, and which are generally tor 3 and retained on inner conductor 1 by means of a spring member 4, which is wound to have the identical pitch as the threads of the aperture 5. Spring 4 is of a cylindrical helical type of circular cross-section having its ends bent slightly inward, forming an elliptical portion which will grip the outside of conductor l and also retain" the insulator in a desired position on the conductor, thus making an integral unit of the as- The process of assembling insulators of this invention to form a concentric conductor is accomplished by employing a special screw driverlocated within an outer tubular metallic c0nduc-' like tool (not shown) to screw spring 4 into the threaded aperture 5 of insulator 2. The assembly comprising spring 4 and insulator 2 which is then pushed over the conductor 8 which raises the outer ends of spring 4 and frictionally locks insulator 2 upon conductor I. When the proper number of insulators are placed on conductor l and spaced in their desired relationship, outer conductor 3 is then slipped over the entire assembly. I

It will be seen that by the use of such a retaining member that the contour of the inner conductor is but slightly enlarged. Likewise, the construction is such that only a small amount of solid dielectric material will be needed to hold the spring and insulator on theinner conductor. Also, at any future time, should it be deemed necessary, the spaced relationship between the various insulators can be conveniently changed without employing any tools.

Although only one embodiment of this invention is shown, it is to be distinctly understood that it is not to be limited in form. For example, various other shapes of insulators may be employed than that of the disc-shaped members 2 shown in the drawing.

What is claimed is:

A transmission line comprising an inner conductor, an outer tubular conductor concentric with the inner 'conductor and a plurality of disc-shaped insulatorsspaced from each other along the inner conductor for spacing said conductorsapart, means for mounting each of said insulators on the inner conductor, said means comprising a threaded aperture in each insulator in which the inner conductor is located and a helical spring for each insulator, said spring surrounding and frictionally engaging the inner conductor and having its convolutions screwed into the threads or the insulator.

2. A transmission line comprising an inner conductor, an outer tubular conductor concentrio with the inner conductor and a plurality of disc-shaped insulators spaced from each other along the inner conductor for spacing said conductors apart, means for mounting each of said insulators on the inner conductor, said means comprising a threaded aperture in each insulator in which the inner conductor is located and a helical spring for each insulator, said spring being slightly smaller in diameter at each end thereof, said spring surrounding and frictionally engaging the inner conductor and having its convolutions screwed into the threads of the insulatorl 3. A transmission line comprising an inner conductor, an outer tubular conductor concentric with the inner conductor and a plurality of discshaped insulators spaced from each-other along the inner conductor for spacing said conductors apart, means for mounting each of said insulators on the inner conductor, said means com prising a threaded aperture in each insulator in which the inner conductor is located and a helical spring for each insulator, said spring being slightly smaller in diameter and bent to form an elliptical contour at each end thereof, said spring surrounding and irictionally engaging the inner conductor and having its convolutions screwed into the threads of the insulator.

4. A transmission line comprising an inner conductor, an outer tubular conductor concentric with the inner conductor and a plurality of discshaped insulators having a rounded outer periphery, said insulators being spaced from each other along the inner conductor for spacing said conductors apart, means for mounting each oi said insulators on the inner conductor, said means comprising a threaded aperture in each insu1ator in which the inner conductor is located and a helical spring for each insulator, said spring being bent slightly smaller in diameter at each end thereof, said spring surrounding and frictionally engaging the inner conductor and having its convolutions screwed into the threads of the insulator.

5. A transmission line comprising an inner conductor; an outer tubular conductor concentric with. the inner conductor and a plurality of disc-shaped insulators having a rounded outer periphery, said insulators being spaced from each other along the inner conductor for spacing said conductors apart, means formounting each of said insulators on the inner conductor, said means comprising a threaded aperture in each insulator in which the inner conductor is located and a helical spring for each insulator, said spring having the same pitch as the threads of the aperture in said insulator, said spring surrounding and irictionally engaging the inner conductor and having its ccnvolutions screwed into the threads of the insulator.

LUDWIG A. esrrsnmsmr. 

